Struvite recovery: pilot-scale results and economic assessment of different scenarios

Abstract

A pilot study was carried out in a waste water treatment plant (WWTP) to recover phosphorous by Struvite precipitation from anaerobic digester centrate by means of Ostara's Pearl technology with the objective to assess technically and economically the performance and reliability of this process treating sidestreams with different concentrations of phosphorous and also to assess the quality of the fertilizer obtained. Different scenarios were studied: phosphorous inlet ranged from 31 to 150 mg PO4-P/L. The phosphorous removal varied from 60 to 81% depending on the influent, and the quality of the Struvite obtained was suitable to be used as a fertilizer. The economic assessment of implementing Struvite Pearl recovery process at full scale in WWTPs with anaerobic digestion (AD) and P-physicochemical or bio-P removal was carried out, taking into account investment (CAPEX) and operating costs (OPEX) of the Struvite recovery process and the economic savings due to phosphorous and ammonium removal in centrates. The results showed that with the current reagent strategies and investment costs, the Struvite recovery process was not economically feasible for WWTPs with AD and P-physicochemical removal. However, in the case of bio-P removal WWTPs with AD, the process can be an economic solution (pay back between 5 and 10 years, OPEX recovered due to the selling Struvite) which creates a high value re-cycled fertilizer and saves the environment due to the higher efficiency of the fertilizer usage.